Wired parallel operation method applied to grid connection and grid disconnection of energy storage system

Abstract

The present invention relates to the technical field of energy storage. Disclosed is a wired parallel operation method applied to grid connection and grid disconnection of an energy storage system. The energy storage system comprises a plurality of inverters, a communication module, an electric meter and a load. The inverters are connected in parallel, each inverter being connected to the communication module, and each inverter being connected to a battery; the electric meter is connected to one of the inverters, and the electric meter is connected to the load. The method comprises: each inverter determines whether the inverter itself is a master inverter or a slave inverter according to the communication state with the electric meter; the master inverter sends a synchronization signal to each slave inverter, such that the switching frequency and the working mode of each slave inverter are synchronized with that of the master inverter; the master inverter communicates with the electric meter to acquire load power consumption information and outputs same to the communication module; and the communication module communicates with the master inverter and the slave inverters to acquire battery information, and adjusts the battery charge and discharge power according to the load power consumption information and the battery information. The present application ensures a reasonable distribution of power among inverters, thus avoiding the phenomenon of high-frequency circulating currents.

Description

A wired parallel method for grid-connected and off-grid energy storage systems Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a wired parallel connection method for grid-connected and off-grid energy storage systems. Background Art

[0002] With the application of energy storage technology, household, industrial and commercial, and ground-based power station energy storage inverters are increasingly being installed for end-use applications. Household inverters generally have a power of less than 20 kilowatts, offering the advantages of easy installation and moderate power, making them suitable for use in homes, communication base stations, small data centers, and other locations. Industrial and commercial energy storage inverters range in power from 50 kilowatts to several hundred kilowatts, and are primarily used in factories and office buildings. Due to the limited power of a single household energy storage inverter and the increasing demand for power in various locations, two or more energy storage inverters are typically used in parallel to expand capacity and increase power. Furthermore, using two or more energy storage inverters in parallel can improve overall system reliability and redundancy.

[0003] However, the existing parallel use of multiple inverters presents the following two problems: On the one hand, when the system is in a grid-connected state, since each inverter independently controls the power fed back to the grid, the power distribution between the inverters is generally relatively balanced. However, when the system is in an off-grid state, since there is only one load and the energy storage system lacks the function of power distribution and control between the inverters, the output power of the inverter is unstable, which in turn causes system oscillation, resulting in the entire energy storage system being unable to operate stably.

[0004] On the other hand, the carrier wave synchronization of each inverter leads to high-frequency circulating current, which can easily cause the filter circuit components in the inverter to withstand high current stress for a long time and fail. Currently, one way to address this high-frequency circulating current phenomenon is to add an industrial frequency isolation transformer to the output of each inverter, connecting the output terminals of the industrial frequency isolation transformers in parallel to achieve parallel operation. However, the larger industrial frequency transformer not only increases the size and weight, but also increases the cost of the entire system. Another approach is to add a suppression inductor to the output of each inverter. However, this method cannot solve the power distribution and industrial frequency circulating current problems between inverters, and also increases the size and space occupied by the system. Another approach is to use the voltage amplitude frequency droop characteristic control in the control algorithm. By adjusting the phase and amplitude of the inverter output voltage, the active power and reactive power of the inverter are evenly distributed. However, this method still cannot effectively solve the high-frequency circulating current problem caused by carrier inconsistency.

[0005] Summary of the Invention

[0006] In order to ensure reasonable power distribution between inverters when multiple inverters are used in parallel in an energy storage system and to avoid high-frequency circulating current, the present application provides a wired parallel method for grid-connected and off-grid energy storage systems.

[0007] The present application provides a wired parallel method for grid-connected and off-grid energy storage systems, employing the following technical solution: the energy storage system comprises a plurality of inverters, a communication module, an electric meter, and a load; the plurality of inverters are connected in parallel, each of which is connected to the communication module; each inverter is connected to a battery; the electric meter is communicatively connected to one of the inverters; and the electric meter is connected to the load. The wired parallel method comprises the following steps:

[0008] S100: The energy storage system is powered on, and each inverter determines whether it is a master inverter or a slave inverter based on the communication status with the electricity meter;

[0009] S200: The master inverter communicates with each slave inverter through the communication module to obtain status information of each slave inverter, and sends a carrier synchronization signal and a status synchronization signal to each slave inverter;

[0010] S300: Each slave inverter performs carrier synchronization according to the carrier synchronization signal to achieve synchronization of the switching frequency with the master inverter; each slave inverter performs self-test according to the status synchronization signal to achieve synchronization of the working mode with the master inverter;

[0011] S400: The host inverter obtains load power usage information by communicating with the power meter and outputs the load power usage information to the communication module;

[0012] S500: The communication module communicates with the master inverter and each slave inverter respectively to obtain battery information corresponding to the master inverter and each slave inverter respectively, wherein the battery information includes battery charge and discharge status and battery SOC;

[0013] S600: The communication module allocates the battery charge and discharge power according to the load power information and battery information, and sends a scheduling instruction to the master inverter and / or the slave inverter according to the allocation result, so that the master inverter and / or the slave inverter controls the adjustment of the corresponding battery charge and discharge power according to the scheduling instruction.

[0014] By adopting the above technical solution, the master inverter sends a carrier synchronization signal and a status synchronization signal to the slave inverter, thereby realizing synchronization between the slave inverter and the master inverter, solving the high-frequency circulating current and power frequency circulating current phenomenon when multiple inverters are connected in parallel, and extending the service life of the inverter; moreover, the method of the present application makes it unnecessary to manually set the selected master inverter on the screen when multiple inverters are used in parallel, and each inverter can automatically identify and determine the master inverter and the slave inverter, and then realize centralized monitoring of multiple inverters and control of each inverter through the communication module. The power distribution and scheduling of the battery makes the charging and discharging power distribution between the inverters reasonable, thus ensuring the stable operation of the energy storage system in both grid-connected and off-grid states. In addition, when the energy storage system is expanded, the host inverter can be used to achieve carrier synchronization and state synchronization of the expanded inverter in the same way. The communication module can be used to manage the expanded inverter and reasonably distribute the power of the expanded battery, which is conducive to the rapid expansion of the energy storage system and keeps the expanded energy storage system in stable operation, avoiding high-frequency circulating current and power-frequency circulating current.

[0015] In a specific implementation scheme, before step S200, the following steps are further included:

[0016] The master inverter communicates with each slave inverter through the communication module and obtains the data packets sent by each slave inverter;

[0017] The master inverter determines the operating status of each slave inverter according to the data packet;

[0018] The master inverter sends a shutdown command or a wait command to each slave inverter according to the operating status of each slave inverter, so that each slave inverter actively exits the energy storage system or enters the wait mode.

[0019] Through the above technical solution, the abnormally operating slave inverter is promptly controlled to exit from the system, thereby avoiding affecting the communication between the master inverter and other slave inverters in the energy storage system, thereby improving the stability of the system.

[0020] In a specific implementation scheme, step S600 specifically includes:

[0021] If the battery is in a discharging state and the battery SOC is inconsistent, the communication module allocates the battery discharge power according to the load power consumption information, and sends a discharge power increase instruction to the host inverter and / or slave inverter corresponding to the battery with a larger SOC according to the allocation result, so that the discharge power of the battery with a larger SOC is increased, or sends a discharge power reduction instruction to the host inverter and / or slave inverter corresponding to the battery with a smaller SOC, so that the discharge power of the battery with a smaller SOC is reduced.

[0022] By adopting the above technical solution, when the battery is in a discharging state and the battery SOCs are inconsistent, the communication module redistributes the battery discharge power by increasing the discharge power of the battery with a large SOC and reducing the discharge power of the battery with a small SOC, so that the SOCs of the batteries eventually tend to be consistent, thereby ensuring stable operation of the system.

[0023] In a specific implementation scheme, step S600 further includes:

[0024] If the battery is in a charging state and the battery SOC is inconsistent, the communication module allocates the battery charging power according to the load power consumption information, and according to the allocation result, sends a charging power reduction instruction to the host inverter and / or slave inverter corresponding to the battery with a larger SOC, so that the charging power of the battery with a larger SOC is reduced, or sends a charging power increase instruction to the host inverter and / or slave inverter corresponding to the battery with a smaller SOC, so that the charging power of the battery with a smaller SOC is increased.

[0025] By adopting the above technical solution, when the battery is in a charging state and the battery SOC is inconsistent, the communication module reallocates the battery charging power. By reducing the charging power of the battery with a large SOC and increasing the charging power of the battery with a small SOC, the SOC of each battery eventually tends to be consistent, thereby ensuring stable operation of the system.

[0026] In a specific implementation scheme, step S600 further includes:

[0027] If the battery is in a discharging state and the battery SOC is consistent, the communication module allocates the battery discharge power according to the load power consumption information, and sends a discharge power consistency instruction to the master inverter and the slave inverter according to the allocation result to make the battery discharge power consistent.

[0028] By adopting the above technical solution, when the batteries are in a discharging state and the battery SOCs are consistent, the communication module redistributes the battery discharge power so that the discharge power of all batteries remains consistent, thereby ensuring stable operation of the system.

[0029] In a specific implementation scheme, step S600 further includes:

[0030] If the battery is in a charging state and the battery SOC is consistent, the communication module allocates the battery charging power according to the load power consumption information, and sends a charging power consistency instruction to the master inverter and the slave inverter according to the allocation result to make the battery charging power consistent.

[0031] By adopting the above technical solution, when the batteries are in a charging state and the battery SOCs are consistent, the communication module redistributes the battery charging power so that the charging power of all batteries remains consistent, thereby ensuring stable operation of the system.

[0032] In a specific possible implementation scheme, the master inverter sends a carrier synchronization signal to each slave inverter at a zero-crossing point of the grid signal;

[0033] Each slave inverter performs carrier synchronization according to the carrier synchronization signal to achieve synchronization with the switching frequency of the master inverter. Specifically, each slave inverter performs carrier synchronization at the zero crossing point of the grid signal according to the carrier synchronization signal to achieve synchronization with the switching frequency of the master inverter.

[0034] By adopting the above technical solution, the anti-interference ability of the signal is improved, the misjudgment of the slave inverter caused by errors in signal transmission is avoided, and it is ensured that the slave inverter can accurately identify the carrier synchronization signal.

[0035] In a specific possible implementation scheme, each slave inverter performs self-test according to the state synchronization signal to achieve synchronization with the working mode of the master inverter, specifically:

[0036] Each slave inverter determines the number of rising edges or falling edges in the state synchronization signal based on the state synchronization signal, and obtains the working mode corresponding to the state synchronization signal based on the number of rising edges or falling edges. Each slave inverter adjusts according to the working mode to achieve synchronization with the working mode of the master inverter; the working mode corresponding to the state synchronization signal represents the working mode of the master inverter.

[0037] By adopting the above technical solution, by determining the number of rising edges or falling edges in the state synchronization signal, the working mode corresponding to the state synchronization signal can be distinguished, thereby improving the reliability of signal transmission.

[0038] In a specific possible implementation scheme, the energy storage system further includes an isolation chip, and each inverter is connected to the communication module via the isolation chip;

[0039] The isolation chip is used to achieve electrical isolation between each inverter and the communication module.

[0040] By adopting the above technical solution, the isolation chip realizes electrical isolation between each inverter and the communication module, thereby improving the safety of the energy storage system.

[0041] In a specific implementation scheme, the operating modes of the host inverter include: grid-connected mode, bypass mode, grid-connected to off-grid mode, off-grid to grid-connected mode, off-grid start-up mode, fault mode, waiting mode, and burning mode. One or more of the following.

[0042] In summary, the technical solution of this application includes at least the following beneficial technical effects:

[0043] 1. The wired parallel method of the present application realizes synchronization between the slave inverter and the master inverter by sending a carrier synchronization signal and a status synchronization signal from the master inverter to the slave inverter, thereby solving the high-frequency circulating current and power frequency circulating current problems when multiple inverters are connected in parallel and extending the service life of the inverter;

[0044] 2. The wired parallel method of the present application eliminates the need to manually select a master inverter on the screen when multiple inverters are used in parallel. Each inverter can automatically identify and determine the master inverter and the slave inverter. The communication module then implements centralized monitoring of multiple inverters and power distribution and scheduling of each battery, ensuring a reasonable distribution of charge and discharge power between the inverters, thereby ensuring stable operation of the energy storage system in both grid-connected and off-grid states.

[0045] 3. The wired parallel method of the present application can also realize carrier synchronization and state synchronization of the expanded inverter through the host inverter in the same way when the energy storage system is expanded, and realize management of the expanded inverter and reasonable allocation of the expanded battery power through the communication module, which is conducive to the rapid expansion of the energy storage system and keeps the expanded energy storage system in stable operation, avoiding high-frequency circulation and industrial frequency circulation phenomena. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] FIG1 is a main flow chart of a wired parallel method according to an embodiment of the present application;

[0047] FIG2 is a schematic diagram of adding a transformer at the output end of an inverter in the prior art;

[0048] FIG3 is a schematic diagram of adding a suppression inductor at the output end of an inverter in the prior art;

[0049] FIG4 is a schematic diagram of the overall structure of the energy storage system in an embodiment of the present application;

[0050] FIG5 is a waveform diagram of a carrier synchronization signal and a grid signal in an embodiment of the present application;

[0051] FIG6 is a timing diagram of the working mode corresponding to the state synchronization signal in an embodiment of the present application. DETAILED DESCRIPTION

[0052] In order to make the objectives, technical solutions and advantages of this application clearer, the implementation methods of this application will be further described in detail below with reference to the accompanying drawings.

[0053] 2 and 3 , FIG2 is a schematic diagram of adding a transformer to the output end of the inverter to solve the high-frequency circulating current phenomenon in the prior art. However, this approach increases the volume and weight of the system and increases the cost. FIG3 is a schematic diagram of adding a suppression inductor to the output end of the inverter to solve the high-frequency circulating current phenomenon in the prior art. However, this approach increases the volume and space of the system and fails to solve the power distribution and power frequency circulating current problems between inverters.

[0054] Therefore, the present application discloses a wired parallel method for grid-connected and off-grid energy storage systems. Referring to Figure 4, the energy storage system includes multiple inverters, a communication module, an electric meter, and a load; the multiple inverters are connected in parallel, and each inverter is connected to the communication module; each inverter is connected to a battery; the electric meter is communicatively connected to one of the inverters, and the electric meter is connected to the load.

[0055] Furthermore, each inverter can be connected to the corresponding battery in a CAN communication mode, each inverter can be connected to the communication module in a CAN communication mode, and the electric meter and the inverter can be connected to each other in an RS485 communication mode. Referring to FIG1 , the wired parallel method includes the following steps:

[0056] S100: The energy storage system is powered on, and each inverter determines whether it is a master inverter or a slave inverter based on the communication status with the electricity meter;

[0057] Specifically, the inverter that successfully communicates with the meter determines itself as the master inverter, and the inverter that fails to communicate with the meter determines itself as the slave inverter. There can be one master inverter and one or more slave inverters.

[0058] S200: The master inverter communicates with each slave inverter through the communication module, obtains status information of each slave inverter, and sends a carrier synchronization signal and a status synchronization signal to each slave inverter.

[0059] Specifically, the master inverter may transmit a carrier synchronization signal and a status synchronization signal to each slave inverter using an IO signal. The status information of the slave inverter may include an operating mode of the slave inverter. The operating mode of the slave inverter may include one or more of: grid-connected mode, bypass mode, grid-connected to off-grid mode, off-grid to grid-connected mode, off-grid startup mode, fault mode, standby mode, and programming mode.

[0060] S300: Each slave inverter performs carrier synchronization according to the carrier synchronization signal to achieve synchronization with the switching frequency of the master inverter; each slave inverter performs self-inspection according to the status synchronization signal to achieve synchronization with the working mode of the master inverter.

[0061] The master inverter and each slave inverter have a transceiver circuit for carrier synchronization signals and status synchronization signals. When the master inverter sends a signal, the slave inverter receives the signal.

[0062] Specifically, during carrier synchronization signal transmission, in order to improve the signal's anti-interference capability, avoid signal transmission errors that may lead to misjudgment of the slave inverter, and ensure that the slave inverter can recognize the carrier synchronization signal, in the above step S200, the master inverter may send a carrier synchronization signal to each slave inverter at the zero-crossing point of the grid signal; in the above step S300, each slave inverter may perform carrier synchronization according to the carrier synchronization signal to achieve synchronization with the switching frequency of the master inverter, which may be: each slave inverter performs carrier synchronization according to the carrier synchronization signal at the zero-crossing point of the grid signal to achieve synchronization with the switching frequency of the master inverter.

[0063] The energy storage system may also be connected to a public power grid. Specifically, the master inverter and the slave inverter obtain power grid signals by connecting to the public power grid.

[0064] Referring to Figure 5, the master inverter sends a carrier synchronization signal at the zero point of the grid signal, and at the same time, each slave inverter also performs a carrier synchronization operation at the zero point of the grid signal after receiving the carrier synchronization signal; further, the carrier synchronization signal includes a low level and a high level, and the low level time in the carrier synchronization signal can be set shorter to ensure that the carrier synchronization signal can be identified and has a strong anti-interference ability. Preferably, the low level time can be set to 2us.

[0065] Specifically, when the status synchronization signal is transmitted, in order to distinguish the working mode corresponding to the status synchronization signal and improve the reliability of signal transmission, each slave inverter can determine the number of rising edges or falling edges in the status synchronization signal according to the status synchronization signal sent by the master inverter, and obtain the working mode corresponding to the status synchronization signal according to the number of rising edges or falling edges. Each slave inverter adjusts according to the working mode to achieve synchronization with the working mode of the master inverter; the working mode corresponding to the status synchronization signal represents the working mode of the master inverter.

[0066] In particular, each slave inverter may include a controller, and the controller is used to receive and identify the number of rising edges or falling edges in the status synchronization signal.

[0067] Referring to Table 1 and Figure 6, a method of distinguishing working modes by determining the number of falling edges in the state synchronization signal can be used. The working modes of the host inverter may include: grid-connected mode, bypass mode, grid-connected to off-grid mode, off-grid to grid-connected mode, off-grid startup mode, fault mode, waiting mode, and one or more of the following modes. Other modes may also be included. Those skilled in the art may design them according to actual conditions, and this application does not impose any restrictions on this. Table 1 shows the number of falling edges corresponding to a working mode and the corresponding meaning of each working mode. Of course, those skilled in the art may also design the number of falling edges for different working modes, or use different numbers of rising edges to distinguish different working modes, and this application does not impose any restrictions on this.

[0068] Table 1 Different working modes, coding rules and corresponding meanings

[0069] Referring to Figure 6, which shows a waveform diagram corresponding to Table 1, the period of sending the state synchronization signal can be set to 100 μs, and the duration of a low-level pulse signal can be set to 4 μs. Each slave inverter determines its corresponding operating mode based on the number of falling edges within a state synchronization signal period.

[0070] S400: The host inverter obtains load power usage information by communicating with the power meter, and outputs the load power usage information to the communication module.

[0071] S500: The communication module communicates with the master inverter and each slave inverter respectively to obtain battery information corresponding to the master inverter and each slave inverter respectively, wherein the battery information includes battery charge and discharge status and battery SOC (State of Charge).

[0072] Specifically, in step S500, the communication module can also obtain the operating modes of the master inverter and the slave inverter by communicating with them, thereby determining whether the energy storage system is in an off-grid state or a grid-connected state. For example, when the operating mode of the master inverter and the slave inverter is a grid-connected mode or an off-grid-to-grid-connected mode, the energy storage system is determined to be in a grid-connected state; when the operating mode of the master inverter and the slave inverter is an off-grid startup mode or a grid-connected-to-off-grid mode, the energy storage system is determined to be in an off-grid state.

[0073] S600: The communication module allocates the battery charge and discharge power based on the load power information and battery information, and sends a scheduling instruction to the host inverter and / or the slave inverter based on the allocation result, so that the host inverter and / or the slave inverter control the adjustment of the corresponding battery charge and discharge power according to the scheduling instruction. Specifically, the communication module can send a scheduling instruction to the host inverter based on the allocation result, so that the host inverter controls the adjustment of the corresponding battery charge and discharge power according to the scheduling instruction; it can also send a scheduling instruction to the slave inverter, so that the slave inverter controls the adjustment of the corresponding battery charge and discharge power according to the scheduling instruction; or it can send a scheduling instruction to the host inverter and the slave inverter at the same time, so that the host inverter and the slave inverter control the adjustment of the charge and discharge power of their respective corresponding batteries according to the scheduling instruction.

[0074] Therefore, the master inverter sends a carrier synchronization signal and a status synchronization signal to the slave inverter to achieve synchronization between the slave inverter and the master inverter, solves the high-frequency circulating current and power frequency circulating current phenomenon when multiple inverters are connected in parallel, and prolongs the service life of the inverter; moreover, the wired parallel method of the present application makes it unnecessary to manually set the selected master inverter on the screen when multiple inverters are used in parallel. Each inverter can automatically identify and determine the master inverter and the slave inverter, and then realize centralized monitoring of multiple inverters and power distribution and control of each battery through the communication module. Scheduling makes the charging and discharging power distribution between the inverters reasonable, thereby ensuring that the energy storage system can operate stably in both the grid-connected state and the off-grid state; the wired parallel method of the present application can also realize carrier synchronization and state synchronization of the expanded inverter through the host inverter in the same way when the energy storage system is expanded, and realize the management of the expanded inverter through the communication module, and realize the reasonable distribution of the expanded battery power, which is conducive to the rapid expansion of the energy storage system, and enables the expanded energy storage system to maintain stable operation, avoiding high-frequency circulating current and power frequency circulating current phenomena.

[0075] Specifically, the energy storage system of the present application can also adopt droop control in the control method, adopt voltage amplitude frequency droop characteristic control, adjust the phase and amplitude of the output voltage of the master inverter and the slave inverter, realize the equal distribution of active power and reactive power of the energy storage system, and further improve the stability of the operation of the energy storage system.

[0076] Furthermore, the above step S600 specifically includes:

[0077] If the battery is in a discharging state and the battery SOC is inconsistent, the communication module allocates the battery discharge power according to the load power consumption information, and sends a discharge power increase instruction to the host inverter and / or slave inverter corresponding to the battery with a larger SOC according to the allocation result, so that the discharge power of the battery with a larger SOC is increased, or sends a discharge power reduction instruction to the host inverter and / or slave inverter corresponding to the battery with a smaller SOC, so that the discharge power of the battery with a smaller SOC is reduced.

[0078] Among them, when the battery with a large SOC corresponds to the host inverter, the communication module sends a discharge power increase instruction to the host inverter corresponding to the battery with a large SOC; when the battery with a large SOC corresponds to the slave inverter, the communication module sends a discharge power increase instruction to the slave inverter corresponding to the battery with a large SOC; when the battery with a large SOC corresponds to both a host inverter and a slave inverter, the communication module sends a discharge power increase instruction to both the host inverter and the slave inverter corresponding to the battery with a large SOC; similarly, the communication module sends a discharge power reduction instruction to the host inverter and / or the slave inverter corresponding to the battery with a small SOC, that is, the communication module sends a discharge power reduction instruction to the host inverter corresponding to the battery with a small SOC, or sends a discharge power reduction instruction to the slave inverter corresponding to the battery with a small SOC, or sends a discharge power reduction instruction to the host inverter and the slave inverter corresponding to the battery with a small SOC at the same time.

[0079] Therefore, when the battery is in a discharging state and the battery SOCs are inconsistent, the communication module redistributes the battery discharge power by increasing the discharge power of the battery with a large SOC and reducing the discharge power of the battery with a small SOC, so that the SOCs of each battery eventually tend to be consistent, ensuring stable operation of the system.

[0080] If the battery is in a charging state and the battery SOC is inconsistent, the communication module allocates the battery charging power according to the load power consumption information, and according to the allocation result, sends a charging power reduction instruction to the host inverter and / or slave inverter corresponding to the battery with a larger SOC, so that the charging power of the battery with a larger SOC is reduced, or sends a charging power increase instruction to the host inverter and / or slave inverter corresponding to the battery with a smaller SOC, so that the charging power of the battery with a smaller SOC is increased.

[0081] Among them, the communication module sends a charging power reduction instruction to the host inverter and / or slave inverter corresponding to the battery with a large SOC, that is, the communication module sends a charging power reduction instruction to the host inverter corresponding to the battery with a large SOC, or sends a charging power reduction instruction to the slave inverter corresponding to the battery with a large SOC, or simultaneously sends a charging power reduction instruction to the host inverter and slave inverter corresponding to the battery with a large SOC; the communication module sends a charging power increase instruction to the host inverter and / or slave inverter corresponding to the battery with a small SOC, that is, the communication module sends a charging power increase instruction to the host inverter corresponding to the battery with a small SOC, or sends a charging power increase instruction to the slave inverter corresponding to the battery with a small SOC, or simultaneously sends a charging power increase instruction to the host inverter and slave inverter corresponding to the battery with a small SOC.

[0082] Therefore, when the battery is in a charging state and the battery SOC is inconsistent, the communication module reallocates the battery charging power by reducing the charging power of the battery with a large SOC and increasing the charging power of the battery with a small SOC, so that the SOC of each battery eventually tends to be consistent, ensuring the stable operation of the system.

[0083] If the battery is in a discharging state and the battery SOC is consistent, the communication module allocates the battery discharge power according to the load power consumption information, and sends a discharge power consistency instruction to the master inverter and the slave inverter according to the allocation result to make the battery discharge power consistent.

[0084] Therefore, when the batteries are in a discharging state and the battery SOCs are consistent, the communication module redistributes the battery discharge power so that the discharge power of all batteries remains consistent, ensuring stable operation of the system.

[0085] If the battery is in a charging state and the battery SOC is consistent, the communication module allocates the battery charging power according to the load power consumption information, and sends a charging power consistency instruction to the master inverter and the slave inverter according to the allocation result to make the battery charging power consistent.

[0086] Therefore, when the batteries are in a charging state and the battery SOCs are consistent, the communication module redistributes the battery charging power so that the charging power of all batteries remains consistent, ensuring stable operation of the system.

[0087] Through the above steps, whether the energy storage system is in a grid-connected or off-grid state, the communication module distributes and adjusts the battery charging and discharging power based on the load power consumption information, while ensuring the load power demand. When the battery SOCs are inconsistent, the battery with a large SOC is controlled to increase the discharge power or reduce the charging power, and the battery with a small SOC is controlled to reduce the discharge power or increase the charging power, so that the SOCs of each battery eventually tend to be consistent, reaching a balanced state, and ensuring the stable operation of the energy storage system.

[0088] Among them, the judgment of batteries with large SOC and batteries with small SOC can be made, for example, by using an average value judgment method: the communication module obtains the total SOC of all batteries and the number of batteries based on the battery information corresponding to the host inverter and the slave inverter respectively, and then obtains the battery SOC average value. Then, batteries with SOC higher than the SOC average value can be judged as batteries with large SOC, and batteries with SOC lower than the SOC average value can be judged as batteries with small SOC. For example, a threshold judgment method can also be used: an SOC threshold is preset in the communication module, and batteries with SOC higher than the SOC threshold are judged as batteries with large SOC, and batteries with SOC lower than the SOC threshold are judged as batteries with small SOC. Those skilled in the art can design the judgment conditions for batteries with large SOC and batteries with small SOC on their own, and this application does not impose any restrictions on this.

[0089] Specifically, the energy storage system may also include photovoltaic panels for power generation, and the energy storage system may also achieve energy interaction with the public grid by connecting to the public grid. Specifically, the master inverter and the slave inverter are connected to the public grid, and when the master inverter and the slave inverter are in grid-connected mode or off-grid to grid-connected mode, the energy storage system is in grid-connected state: if the battery is in a charging state, the source of electric energy for charging the battery can be the photovoltaic panel, the public grid, or the photovoltaic panel and the public grid can charge the battery at the same time; if the battery is in a discharging state, the electric energy discharged by the battery can be used by the load, or can be transmitted to the public grid to interact with the public grid, or can be used by the load and transmitted to the public grid at the same time;

[0090] When the master inverter and the slave inverter are in off-grid startup mode or grid-connected to off-grid mode, the energy storage system is in an off-grid state: if the battery is in a charging state, the power source for charging the battery can be the photovoltaic panel; if the battery is in a discharging state, the discharged power of the battery can be used by the load.

[0091] Furthermore, referring to FIG4 , the energy storage system further includes an isolation chip, through which each inverter is connected to the communication module; the isolation chip is used to achieve electrical isolation between each inverter and the communication module, thereby improving the safety of the energy storage system.

[0092] Furthermore, before the above step S200, the following steps are also included:

[0093] The master inverter communicates with each slave inverter through the communication module and obtains the data packets sent by each slave inverter;

[0094] The master inverter determines the operating status of each slave inverter according to the data packet;

[0095] The master inverter sends a shutdown command or a wait command to each slave inverter according to the operating status of each slave inverter, so that each slave inverter actively exits the energy storage system or enters the wait mode.

[0096] Among them, the operating status of each slave inverter includes normal operation and abnormal operation. Specifically, the master inverter sends a shutdown command to the slave inverter with abnormal operation, so that the slave inverter with abnormal operation actively exits from the energy storage system; the master inverter sends a wait command to the slave inverter with normal operation, so that the slave inverter that has not been lost and is operating normally enters the wait mode.

[0097] Furthermore, the host inverter can also determine whether a slave inverter is lost based on the data packet, and mark the lost slave inverter. The lost slave inverter cannot communicate normally with the host inverter, and the host inverter does not send a shutdown command or a wait command to it.

[0098] Specifically, when the master inverter determines whether a slave inverter is lost, it can be done in the following way: when the master inverter cannot obtain the data packet sent by the slave inverter, it can be considered that the slave inverter is lost; when the master inverter determines whether the slave inverter is operating normally, it can be done in the following way: the master inverter determines whether the slave inverter is operating normally based on the content of the data packet sent by each slave inverter.

[0099] Furthermore, the data packet may include: BMS data (BMS, BATTERY MANAGEMENT SYSTEM, battery management system), further, the BMS data is relevant data of the battery management system connected to the slave inverter; it may also include operating data of the slave inverter, further, the operating data of the slave inverter may include device information and operating information of the inverter, battery voltage information, battery current information, battery temperature information, and internal fault information of the slave inverter, off-grid data, etc.; it may also include alarm information, further, the alarm information may include alarm information inside the slave inverter and alarm information of other devices connected to the slave inverter.

[0100] Therefore, by timely controlling the abnormally operating slave inverter to exit the system, the communication between the master inverter and other slave inverters in the energy storage system is avoided, thereby improving the stability of the system.

[0101] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A wired parallel method for connecting to and off-grid energy storage systems, characterized in that: The energy storage system includes multiple inverters, a communication module, an electric meter, and a load; the multiple inverters are connected in parallel, and each inverter is connected to the communication module; each inverter is connected to a battery; the electric meter is connected to a host inverter among the multiple inverters in communication; the electric meter is connected to the load; the wired parallel method includes the following steps: S100: The energy storage system is powered on, and each inverter determines whether it is a master inverter or a slave inverter according to the communication status with the electric meter; the inverter that successfully communicates with the electric meter is the master inverter, and the inverter that fails to communicate with the electric meter is the slave inverter; S200: The master inverter communicates with each slave inverter through the communication module to obtain status information of each slave inverter, and sends a carrier synchronization signal and a status synchronization signal to each slave inverter; S300: each slave inverter performs carrier synchronization according to the carrier synchronization signal to achieve synchronization with the switching frequency of the master inverter; each slave inverter performs self-check according to the state synchronization signal to achieve synchronization with the working mode of the master inverter; S400: the host inverter communicates with the electric meter to obtain load power consumption information, and outputs the load power consumption information to the communication module; S500: The communication module communicates with the host inverter and each slave inverter respectively to obtain battery information corresponding to the host inverter and each slave inverter respectively, wherein the battery information includes a battery charge and discharge state and a battery SOC; S600: The communication module allocates the charge and discharge power of the battery according to the load power information and the battery information, and sends a scheduling instruction to the host inverter and / or the slave inverter according to the allocation result, so that the host inverter and / or the slave inverter controls the adjustment of the charge and discharge power of the corresponding battery according to the scheduling instruction; Each slave inverter performs self-check according to the state synchronization signal to achieve synchronization with the working mode of the master inverter, specifically: Each slave inverter determines the number of rising edges or falling edges in the state synchronization signal according to the state synchronization signal, and obtains the working mode corresponding to the state synchronization signal according to the number of rising edges or falling edges. Each slave inverter adjusts according to the working mode to achieve synchronization with the working mode of the master inverter; the working mode corresponding to the state synchronization signal represents the working mode of the master inverter.

2. The wired parallel method for connecting to and disconnecting from the grid of an energy storage system according to claim 1, characterized in that: Before step S200, the following steps are also included: The master inverter communicates with each slave inverter through the communication module to obtain the data packets sent by each slave inverter; The master inverter determines the operating status of each slave inverter according to the data packet; The master inverter sends a shutdown command or a waiting command to each slave inverter according to the operating status of each slave inverter, so that each slave inverter actively exits from the energy storage system or enters the waiting mode.

3. The wired parallel connection method for grid-connected and off-grid energy storage systems according to claim 1, characterized in that: Step S600 specifically includes: If the battery is in a discharging state and the battery SOC is inconsistent, the communication module uses telecommunication according to the load. The discharge power of the battery is allocated according to the information, and according to the allocation result, a discharge power increase instruction is sent to the host inverter and / or slave inverter corresponding to the battery with a large SOC to increase the discharge power of the battery with a large SOC, or a discharge power reduction instruction is sent to the host inverter and / or slave inverter corresponding to the battery with a small SOC to reduce the discharge power of the battery with a small SOC.

4. The wired parallel connection method for grid-connected and off-grid energy storage systems according to claim 1, characterized in that: Step S600 specifically also includes: If the battery is in a charging state and the battery SOC is inconsistent, the communication module allocates the battery charging power according to the load power consumption information, and sends a charging power reduction instruction to the host inverter and / or slave inverter corresponding to the battery with a larger SOC according to the allocation result, so that the charging power of the battery with a larger SOC is reduced, or sends a charging power increase instruction to the host inverter and / or slave inverter corresponding to the battery with a smaller SOC, so that the charging power of the battery with a smaller SOC is increased.

5. The wired parallel method for grid-connected and off-grid energy storage systems according to claim 1, characterized in that: Step S600 specifically also includes: If the battery is in a discharging state and the battery SOC is consistent, the communication module allocates the battery discharge power according to the load power consumption information, and sends a discharge power consistency instruction to the host inverter and the slave inverter according to the allocation result to make the battery discharge power consistent.

6. The wired parallel method for connecting to and disconnecting from the grid of an energy storage system according to claim 1, characterized in that: Step S600 specifically also includes: If the battery is in a charging state and the battery SOC is consistent, the communication module allocates the battery charging power according to the load power consumption information, and sends a charging power consistency instruction to the host inverter and the slave inverter according to the allocation result to make the battery charging power consistent.

7. The wired parallel method for connecting to and disconnecting from the grid of an energy storage system according to claim 1, characterized in that: The master inverter sends a carrier synchronization signal to each slave inverter at the zero-crossing point of the grid signal; Each slave inverter performs carrier synchronization according to the carrier synchronization signal to achieve synchronization with the switching frequency of the master inverter. Specifically, each slave inverter performs carrier synchronization at the zero crossing point of the power grid signal according to the carrier synchronization signal to achieve synchronization with the switching frequency of the master inverter.

8. The wired parallel method for connecting to and disconnecting from the grid of an energy storage system according to claim 1, characterized in that: The energy storage system further includes an isolation chip, and each inverter is connected to the communication module via the isolation chip; The isolation chip is used to achieve electrical isolation between each inverter and the communication module.

9. The wired parallel method for grid-connected and off-grid energy storage systems according to claim 7, characterized in that: The working modes of the host inverter include: one or more of: grid-connected mode, bypass mode, grid-connected to off-grid mode, off-grid to grid-connected mode, off-grid startup mode, fault mode, waiting mode, and burning mode.

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